Removal of combustion chamber deposits in spark-ignition engines



United States Patent fiice 2,596,805 Patented Dec. 14, 1954 REMOVAL OFCOMBUSTION CHAMBER DEPOSITS IN SPARK-IGNITION ENGINES John Mingle, Jr.,Richmond, Califl, assignor to Califorma Research Corporation, SanFrancisco, Calif a corporation of Delaware No Drawing. ApplicationAugust 7, 1953, Serial No. 373,051

9 Claims. (Cl. 123-1) This invention relates to a method of purging thecombustion chamber of spark-ignition internal combustion engines, andparticularly to a method of removing deposits from the internal parts ofthe combustion chamber Which normally detract from efficient fuelcombustion and decrease the power output in the operation of thespark-ignition internal combustion engines.

It is an accepted fact that normal operation of sparkignition engineswith conventional lubricating oils and gasoline compositions normallyaccumulates organic and inorganic deposits within the combustion chamberand upon the moving parts of the engine. These deposits rapidly reduceengine efiiciency and ultimately require complete dismantling of theengine for a cleansing or replacement of fouled engine parts.

Numerous methods have been proposed by which these carbonaceous depositscould be removed without having to resort to a complete dismantling ofthe engine. These various proposals generally fall within the categoriesof oxidation, solvent action and mechanical removal. Numerous proposalshave been made to inject various solvents into the fuel itself in anattempt to dissolve the deposits during operation of the engine. Othermethods involve the introduction of oxidative catalysts and theapplication of heat to oxidize these deposits. The mechanical and manualmethods which include peening and shot-blasting normally require anexposure of the engine parts to effect a removal of the deposits.

While a number of these methods have achieved a certain measure of theirobjective, namely that of reducing the amount of combustion depositswithout requiring a complete dismantling of the engine, none of thesemethods, with the possible exception of mechanical or manual depositremoval, have removed enough of the combustion deposits to materiallyimprove the performance of the engine and bring the engine efficiencyback to its original potential. In the solvent and certain oxidativeremoval methods whereby the purge process is conducted incidentally toengine operation, all of the proposals continuously stress smooth engineperformance without perceptible knocking.

Contrasting the underlying precepts of these previous proposals, it hasbeen found that effective removal of combustion chamber deposits in aspark-ignition engine may be attained with a negligible modification ofthe mechanical aspects of engine operation by operating the engine for ashort period under conditions of auto-ignition. Thus, it has beendiscovered that by mere substitution for the normal gasoline fuel of anauto-ignitable fuel composition possessing a volatility substantiallywithin the gasoline volatility range and operating the engine thereonunder sufficient loading conditions as to cause auto-ignition, effectivecleansing and purging of the internal surfaces of the combustion chamberand associated moving parts are obtained. In this type of operation,the,combustion deposits are removed through the exhaust system of theengine and the engine is substantially restored to its potentialperformance characteristics.

In conducting this purge method, the auto-ignitable fuel composition ispreferably introduced into the fuel line of the engine preceding thecarburetor as a replacement of the normal gasoline fuel. When operatingthe engine on the auto-ignitable purge fuel, a sufficient load isapplied to the engine either by internal friction and inertia or byexternal loading such as with a dynamometer to cause the fuelcomposition to auto-ignite within the combustion chamber of the engine.

The period of auto-ignition operation required to effect a substantialremoval of the combustion chamber deposits is variable depending uponthe mechanical characteristics of the engine, such as compression ratio,etc., as well as the amount of deposits to be removed. From a practicalstandpoint, the duration of the purging process is controlled simply bythe introduction of a predetermined amount of auto-ignitable fuel.

In the preferred method of conducting the purge process, thespark-ignition engine is disengaged from its external load and ameasured quantity of auto-ignitable fuel is introduced into the fuelline entering the carburetor through gravity flow from an overheadreceptacle. The engine is started up on the purge fluid and operatedunder intermittent full-throttle acceleration with internal enginefriction and inertia as the only load applied until the combustiondeposits are substantially exhausted from the system. Although thenumber of full-throttle accelerations progressively reduces the amountof combustion chamber deposits, it has been found that approximately70-80% of the combustion chamber deposits will have been effectivelyexhausted after about thirty full-throttle openings.

The purge fluid is a fuel composition which is susceptible toauto-ignition under the conditions of operation obtainable in thespark-ignition engine, and possesses a volatility substantially withinthe gasoline volatility range. It has now been determined that foreffective deposit removal, coupled with practical application in theconventional spark-ignition engines, the auto-ignitable purge fluidshould possess an A. S. T. M. octane number at least 35 octane numberslower than the equilibrium octane requirement (EOR) of the engine to bepurged as determined by the conventional test procedure identified asCRC designation E-l-748. As previously indicated, the combustion chamberdeposits gradually accumulate in service with corresponding increase inoctane requirement of the engine until the octane requirement reaches asubstantial equilibrium which, in the case of normal automotive engineoperation, is attained in about 2000 to 3000 miles of driving.

Although, directionally, the lower the octane number and,correspondingly, the higher the cetane number of the purge fluid, thegreater the eificiency in deposit removal over a given period ofauto-ignition engine operation, certain practical limits are dictated inthe case of the more recent high-compression, high-octane requirementengines. In certain of these high output engines, the differentialbetween initial and equilibrium octane requirement is comparativelysmall, and, for a comparable purge efficiency, allow the use of a higheroctane number auto-ignitable purge fluid. It has been found preferablein engines having an EOR above to employ an auto-ignitable p'urge fluidhaving an octane number between about 35 to 60 octane numbers below theEOR of the engine. In the case of engines having an EOR less than 90, itis preferable, for maximum purge efficiency, to employ an auto-ignitablepurge fluid whose octane number is at least 50 octane numbers lower thanthe EOR of the engine.

In order to obtain the maximum effect of this purge method, particularlyfor application in spark-ignition engines with compression ratios of 5.5:1 and above, 1t has been discovered that the auto-ignitable purge fluidshould possess an A. S. T. M. octane number below about 30 and an A. S.T. M. cetane number above about 45. Auto-ignitable fuels satisfying thisoctane-cetane number balance include the low octane, straight chainhydrocarbons and the high cetane, oxygen-containing chemicalsconventionally recognized as cetane-improving agents, as well as blendsthereof in varying proportions, provided the final composition possessesa volatility substantially within the gasoline volatility range. Whenreferring to A. S. T. M. octane numbers and A. S. T. M. cetane numbersthroughout the specification and claims, it is to be understood thatreference is made to octane numbers measured by A. S. T. M. D357-48 andcetane numbers as measured by A. S. T. M. D6l3-48T.

Suitable hydrocarbon fuels which may be used per se or in various blendsthereof are the predominantly straight chain hydrocarbons boiling withinthe gasoline boiling range, such as n-heptane, n-octane,Z-methylheptane, 3- methylheptane, 4-methylheptane, n-nonane, Z-methyloctane, 3-n1ethyl octane, 4-methyl octane, 2,6-dirnethylheptane,l-octene, n-propylcyclopentane, n-propylcyclohexane, and certainselected natural and straight run gasoline stocks. In addition to thehydrocarbon fuels and preferably complementing the higher octane stocks,a group of chemical compounds falling within the recognizedclassification of oxygen-containing cetane-improving agents may beemployed in the auto-ignitable purge fluid. These compounds, whichpossess a high cetane value, are normally used in additive amounts to upade the cetane number of diesel fuel oil stocks and characteristicallypromote precombustion vapor phase oxidation. The principal components ofthis category of compounds are the organic ethers, peroxides, andnitrate esters, of which the following compounds and materials aretypical: methyl isopropyl ether, methyl sec. butyl ether, din-propylether, di-n-butyl ether, di-isoarnyl ether, diethoxyacetone, diethylformaldehyde, 1,2-propyiene glycol diethyl ether, glyceroltri(ethoxyethyl) ether, py-

rogallol trimethyl ether, di-isopropyl polyethylene oxide,

diethyl Carbitol, benzoyl peroxide, benzyl peroxide, peroxideddecahydronaphthalene, diethyl peroxide, mesityl oxide peroxide,trimolecular acetone peroxide, di(tert. butyl) peroxide, cyclohexyl'hydroperoxide, alkyl hydroperoxides, prepared in accordance with Patents2,317,968 and 2,365,220, dialkyl peroxides, prepared in accordance withPatents 2,521,698, 2,522,015, and 2,522,016, amyl nitrate, ethylnitrate, etc.

In preparing a suitable purge fluid to meet the requisite octane-octanenumber balance and volatility, one or more cetane-improving agents maybe blended together and used per se, or in combination with acomparatively high octane gasoline stock. Although the cetane-improviiagents satisfying the volatility requirements may be used per se, it ispreferable to blend these agents with a hydrocarbon fuel stock to obtainbetter starting characteristics in the purge fluid. When usingoctane-improving agents in the compounding of the purge fluid, theoctane number of the base gasoline stock may materially exceed 30.

The composition of the purge fluid is susceptible to considerablevariation within the foregoing specifications and is dependent to agreat extent upon availability and economics of suitable blending stocksand chemical. components. Some of the individual cetane-improvingagents, such as the hi h molecular weight peroxides and hydroperoxidesobtained from the oxidation of kerosene stocks, etc., are notsufficiently volat le to allow satisfactory carburetion for introductionto the engine. These materials may be modified by bending with morevolatile cetaneimproving agents, such as ethyl ether. and/or compoundingwith the more volatie hydrocarbon stocks, such as n-heptane. As anillustration of effective blends of cetaneimproving agents inhydrocarbon stocks, desirable autoignition fluids are obtained byincorporating 20-50% by weight of ethyl ether in n-heptane and 3-10%amyl nitrate in n-heptane.

In automotive spark-ignition engines. the improvements in engineoperation obtained by removal of combustion de osits in accordance withthe subiect process h ve been effectively illustrated by a series ofcomprehensive tests wherein the degree of deposit remov l and efiiciencyof the purge method was defined by differences in octane requirement ofthe engine. In determining these improvements, the automotive engine wassubjected to a standard road octane requirement test conducted inaccordance with the procedure outlined in CRC designation E1748entitled, Research Technique for Determination of Octane NumberRequirements of Vehicles on the Road, both before and after subjectingthe automotive engine to the present purging method. This test isconducted on a series of reference fuels and ascertains the octanenumber of the fuel required for incipient knocking of the engine over astandard road course within the normal speed range of the vehicle.

Test results on a series of automobiles of conventional make andcontemporary manufacture with the subject purge method employingrepresentative purge fluids within the foregoing specifications haveresulted in decreases in octane requirement varying from 2 to 18 octanenumbers, depending upon the type of engine and service history of theengine. In addition to the octane requirement decrease obtained, it wasfound that acceleration times L were consistently improved andrepresented an average power increase of about 4% on 21 test cars.

The following examples serve as an illustration of a number of methodsof applying the subject purging process with certain specificauto-ignitable purge fluids. It is to be understood that these examplesare not to be construed as a limitation of the invention, either withrespect to urge fluid composition or the method of applying theforegoing purge process.

Example I The octane requirement of a 1941 De Soto sedan, with anodometer reading of 34,585 miles was determined on the road inaccordance with standard procedure outlined in CRC E1748, using primaryreference fuels. In order to obtain the octane requirement, the fuelline of the engine was disconnected at the suction side of the fuel pumpand a special inch line run into the cab of the car where the referencefuels were carried. With the timing checked at the standard sparkadvance for a 1941 De Soto, the test procedure was conducted and theoctane requirement determined to be 86. The time required to traverse ameasured test course on a hill starting at 20 M. P. H. was 13.4, and acheck at 13.0 seconds.

In administering the purge treatment, the engine was stopped and thefuel line disconnected at the carburetor. 8 ounces of an auto-ignitablepurge fluid, consisting of a blend of 30% ethyl ether in a straight runMichigan gasoline stock possessing an A. S. T. M. octane number of 23,was introduced into the fuel line preceding the carburetor from aseparate container. The engine was started and as soon as the gasolinein the carburetor was consumed, which was evidenced by initial knocking,the throttle was alternately opened and closed. The engine was operatedin this manner, namely, open throttle for accelerations to about 2500 R.P. M. and closed throttle until the engine slowed down to an idlingspeed of about 450 R. P. M. with no external load applied, for 37throttle openings, of which 32 were at maximum knock intensity. Thistreatment required about two minutes.

The fuel system was then returned to its original position forconducting the octane requirement without adjusting the ignition systemor the timing. The octane requirement after the purge process wasdetermined as 74, and the corresponding acceleration times over the samecourse dropped to 12.4 and 12.7 seconds. The removal of combustionchamber deposits by this purge method resulted in a lowering of theoctane requirement of 12 numbers, and a power increase, as representedby the decrease in acceleration times, of 5.2%.

Example 11 The procedure as outlined in the previous example wasconducted on a 1946 Dodge pick-up truck. The initial octane requirementwas determined as 70, and the accheck 14.1 seconds; and on the southcourse 17.2 check 14.9 check 14.1 seconds. The application of the purgemethod resulted in a decrease in octane requirement of 11 numbers, and apower increase of 9.6%.

Example III The purge method was applied to a stationary L-head CPRengine. In this test combustion chamber deposits were built up byoperating the engine on commercial gasoline and lubricating oil for aperiod of 265 hours, corresponding to about 5000 miles of automotiveengine operation. The equilibrium octane requirement of the engine wasthen determined by supplying the engine successively with reference fuelblends until the rating level knock was observed. Commercial diethylether was carbureted to the engine for 15 minutes at normal fuel-airratio. The engine operating conditions were as follows: 900 R. P. M.,6.8 to 1 compression ratio, F. jacket coolant temperature, 75 'F. intakemanifold temperature, 4 B. T. C. ignition timing, full throttle. Theengine operated immediately under conditions of auto-ignition uponadmitting the ether into the manifold. Auto-ignition was evidenced bycharacteristic sound, key-01f ignition, and observation of the diagramon an oscilloscope. After 15 minutes of operation on the diethyl ether,the octane requirement of the engine was determined in the same manneras previously stated. The octane requirement of the engine immediatelyprior to application of the purge process was 81. After 15 minutes ofoperation under auto-ignit on conditions on the diethyl ether purgefluid, the octane requirement was reduced to 45. The clean engine octanerequirement was established to be 33.

Example IV In this test, the purge method was applied to a 1950 Buicksedan which had been operated for 3521 miles on commercial fuel andlubricating oil. The initial octane requirement of the engine wasdetermmed as outlined in Example I and found to be 88. Contrasting theprocedures of Examples I with II, wherein the purge method was employedunder no-load conditions, in this test the purge fluid was applied tothe engine under conditions of external load or under road operation.

The purge fluid was composed of n-heptane compounded with 20% by weightof concentrated dialkyl peroxides, in which the alkyl groups averagedabout C10. The cetane-improving agent was obtained by acid treating aperoxidized kerosene stock within the bo1l1ng range of about 300-370" F.as described in U. S. Patents 2,521,698, 2,522,015 and 2,522,016. Afterthis purge fluid was admitted to the carburetor, five fullthrottleaccelerations from -60 M. P. H. were made with keyoif ignition. Therewas good acceleration and good engine operation on the first twoaccelerations. On the third, acceleration from 2030 M. P. H wassluggish. On the fourth, there was one cylinder misfirmg, and on thefifth there was no ditference in acceleration w1th ignition key on oroff. After five accelerations over the test course, the engine wasswitched to the primary reference fuels to determine the octanerequirement. The octane requirement was determined to be 8 3.

Following this test cycle, the purge fluid was again admitted to thecarburetor, and five passes of the test course were made, with severalfull-throttle accelerations per pass. Again the octane requirement wasdetermined and found to be 82. At the completion of the test, thecylinder head of the engine was removed and the combustion chamberinspected and found to be exceptionally clean, with no deposits. Therewas a small amount of powder on the exhaust valves and the spark plugswere undamaged.

The engine was disassembled and the exhaust valves and entire combustionchamber surfaces were manually cleaned by scraping and wire brushing.The octane number of the cleaned engine was determined and found to be80.

Example V The purge process as outlined in Example I was conducted on a1953 Cadillac which had been operated for 4072 miles on commercial fueland lubricating oil. The octane requirement of the engine as determmedin accordance with CRC E1-748 was 93. The purge treatment, employing asthe auto-ignitable purge fluid 35% iso-octane in normal heptane, wasadministered and 30 full-throttle no-load accelerations were applied. Atthe conclusion of the treatment, the octane requirement was determinedto be 91.

In order to determine the effectiveness of the purge process, the enginewas dismantled and mechanlcally cleaned. The octane requirement of themechanicallycleaned engine was found to be 90, indicating an octanerequirement increase for the period of operation of 3 octane numbers, 2of which were removed by a s ngle purge treatment with a 35 octanenumber purge fluid.

Example VI In ascertaining the eifect of octane number level in theauto-ignitable purge fluid, the following experiment was conducted on a1953 Buick which had been operated on conventional fuel for 4174 miles.

The octane requirement of the engine after this period of operation wasdetermined to be 91 and a purge treatmentwas administered similar tothepreceding example employing as the purge fluid a mixture of 60%iso-octane in normal heptane. At the conclusion of the treatment,namely, after 30 no-load full-throttle openings, the octane requirementof the engine was determined to be /2, indicating no significantreduction in the combustion chamber deposits. The engine was againpurged in a similar manner employing 35% iso-octane in normal heptane asthe purge fluid. At the conclusion of this treatment, the octanerequirement of the engine was determined to be 87 /2, whereas the enginein a mechanically-cleaned condition hadan octane requirement of 86.

Example VII A further comparison of the effectiveness of the subjectprocess, particularly with respect to engines of low octane requirementincrease, was conducted on a 1950 Buick whose engine had an equilibriumoctane requirement of 85. On level road acceleration tests from 2060 M.P. H. in high gear, the acceleration times averaged 12.6 seconds. Thisengine was subjected to the conventional purge treatment with a 60octane number purge fluid. At the conclusion of this treatment, theoctane requirement of the engine remained at 85, indicating no effectupon the combustion chamber deposits and the acceleration times averaged12.5 seconds.

In a second purge treatment, a 45 octane number purge fluid was employedresulting in a drop in octane requirement of the engine to 83 with acorresponding reduction in acceleration times to 12.0, indicating a 5%power increase. The octane requirement of this engine in amechanically-cleaned condition was determined to be 82.

Similarly, a 1950 Buick having an equilibrium octane requirement of 89was purged with a 30 octane number purge fluid to an 86 octanerequirement with a substantially clean engine octane requirement of 85.

This application is a continuation-in-part of my application, Serial No.203,220, filed December 28, 1950, entitled Removal of Combustion ChamberDeposits in Spark Ignition Engines," and now abandoned.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and only such limitations should be imposed as areindicated in the appended claims.

I claim:

1. A method of removing combustion chamber deposits in a spark-ignitioninternal combustion engine which comprises introducing into the fuelline preceding the carburetor of said engine as the sole fuel anauto-ignitable fuel composition whose volatility is substantially withinthe gasoline volatility range and possessing an A. S. T. M. octanenumber at least 35 octane numbers lower than the equilibrium octanerequirement of said engine, and operating said engine with said fuelcomposition under loading conditions sufiicient to cause auto-ignitionuntil the exhaust system is noticeably free of the purged combustionchamber deposits.

2. A method of removing combustion chamber deposits in a spark-ignitioninternal combustion engine which comprises introducing into the fuelline preceding the carburetor of said engine an auto-ignitable fuelcomposition whose volatility is substantially within the gasolinevolatility range and possessing an A. S. T. M. octane number at least 35octane numbers lower than the equilibrium octane requirement of saidengine, and operating said engine with said auto-ignitable fuelcomposition in the absence of external load under intermittentfullthrottle acceleration until the exhaust system is noticeably free ofthe purged combustion chamber deposits.

3. A method of removing combustion chamber deposits in a spark-ignitioninternal combustion engine which comprises introducing into the fuelline preceding the carburetor of said engine an auto-ignitable fuelcomposition whose volatility is substantially within the gasolinevolatility range and possessing an A. S. T. M. octane number at least 35octane numbers lower than the equilibrium octane requirement of saidengine, and operating said engine with said auto-ignitable fuelcomposition in the absence of external load under intermittentfullthrottle acceleration for at least 30 throttle openings.

4. A method of removing combustion chamber deposits m a spark-ignitioninternal combustion engine which comprises introducing into the fuelline preceding the carburetor of said engine as the sole fuel anauto-ignitable fuel composition possessing an A. S. T. M. octane numberbelow 30 and an A. S. T. M. cetane number above 45, which fuel possessesa volatility substantially within the gasoline volatility range, andoperating said engine with said fuel composition under loadingconditions sufficient to cause auto-ignition.

5. A method of removing combustion chamber deposits in a spark-ignitioninternal combustion engine which comprises introducing into the fuelline preceding the carburetor of said engine an auto-ignitable fuelcomposition whose volatility is substantially within the gasolinevolatility range and possessing an A. S. T. M. octane number below 30and an A. S. T. M. cetane number above 45, and operating said enginewith said fuel composition in the absence of external load underintermittent full-throttle acceleration.

6. A method of removing combustion chamber deposits in a spark-ignitioninternal combustion engine which comprises introducing into the fuelline preceding the carburetor of said engine an auto-ignitable fuelcomposition whose volatility is substantially within the gasolinevolatility range and possessing an A. S. T. M.

octane number below 30 and an A. S. T. M. cetane numposition whosevolatility is substantially within the gasoline volatility range andpossessing an A. S. T. M. octane number below 30 and an A. S. T. M.cetane number above 45, and comprising a petroleum distillate fractionof low octane number in combination with at least one organic vaporphase oxidation promoter selected from the group consisting of organicnitrates, organic peroxides, and organic ethers capable of materiallyimproving the cetane number of said petroleum distillate fraction, andoperating said engine with said fuel composition in the absence ofexternal load under intermittent full-throttle acceleration.

8. A method of removing combustion chamber deposits in a spark-ignitioninternal combustion engine which comprises introducing into the fuelline preceding the carburetor of said engine an auto-ignitable fuelcomposition whose volatility is substantially within the gasolinevolatility range and possessing an A. S. T. M. octane number below 30and an A. S. T. M. cetane number above 45, and comprising a petroleumdistillate fraction of low octane number in combination with at leastone organic vapor phase oxidation promoter selected from the groupconsisting of organic nitrates, organic peroxides, and organic etherscapable of materially improving the cetane number of said petroleumdistillate fraction, and operating said engine with said fuelcomposition in the absence of external load under intermittentfull-throttle acceleration conditions for at least 30 accelerations.

9. A method of removing combustion chamber deposits in a spark ignitioninternal combustion engine which comprises substituting for the normalgasoline fuel and introducing into the fuel line preceding thecarburetor an auto-ignitable fuel composition possessing an A. S. T. M.octane substantially below said normal gasoline fuel and a substantiallypositive A. S. T. M. octane number, said auto-ignitable fuel compositionfurther possessing a volatility substantially, within the gasolinevolatility range, and operating said engine with said autoignitable fuelcomposition in the absence of external load under intermittentfull-throttle acceleration until the exhaust system is noticeably freeof the purged combustion chamber deposits.

No references cited.

1. A METHOD OR REMOVING COMBUSTION CHAMBER DEPOSITS IN A SPARK-IGNITIONINTERNAL COMBUSTION ENGINE WHICH COMPRISES INTRODUCING INTO THE FUELLINE PRECEDING THE CARBURETOR OF SAID ENGINE AS THE SOLE FUEL ANAUTO-IGNITABLE FUEL COMPOSITION WHOSE VOLATILITY IS SUBSTANTIALLY WITHINTHE GASOLINE VOLATILITY RANGE AND POSSESSING AN A.S.T.M. OCTANE NUMBERAT LEAST 35 OCTANE NUMBERS LOWER THAN THE EQUILIBRIUM OCTANE REQUIREMENTOF SAID ENGINE, AND OPERATING SAID ENGINE WITH SAID FUEL COMPOSITIONUNDER LOADING CONDITIONS SUFFICIENT TO CAUSE AUTO-IGNITION UNTIL THEEXHAUST SYSTEM IS NOTICEABLY FREE OF THE PURGED COMBUSTION CHAMBERDEPOSITS.